Pressure actuated assemblies that are designed to selectively actuate a subterranean tool typically involves a ball seat and a ball that is dropped or pumped to the ball seat and landed. Once the ball is landed internal pressure is built up through a wall opening to a piston housing surrounding the main bore so that a tool can be actuated. Typically a piston receives the internal pressure through a wall port and has an opposite end referenced to annulus pressure. Raising the tubing pressure moves the piston which actuates the tool. In one example of a liner hanger, the piston can move slips and a sealing element to support a liner from a surrounding casing.
There can be issues with such a design. The tool can be in a long horizontal run so that it may take the ball a long time to get to the seat without having to be pumped. In a horizontal run the ball may not locate on the seat even with a flowing stream urging the ball to the seat. Wall openings to piston housings can also present potential leak paths if seals deteriorate or fail.
Accordingly, an actuation system is needed that can be selectively operated from a remote location to operate a tool at the desired location. In the preferred embodiment an actuation system is described that locks in potential energy with a lock that is disabled to release the potential energy to set the tool. In a preferred application a liner hanger slip system and seal can be set with the device. The lock is defeated with physical movement that is induced with an applied field or with an electromechanical device to name a few preferred options. In one embodiment the field is magnetic and the lock release is accomplished with a repelling response to a magnet that serves at least in part as a locking key and whose movement results in a release of the potential energy force. Those skilled in the art will better appreciate aspects of the preferred embodiments of the invention from a review of the description of the preferred embodiment and the associated FIGS. while recognizing that the full scope of the invention is to be found in the appended claims.
U.S. Pat. No. 7,703,532 illustrates moving a magnet in position to hold open a flapper in a safety valve in the open position and to reduce its tendency to chatter in the open position. US Publication 2009/0032238 illustrates a magnet used to assist the movement of a flapper in a safety valve to go to an open position by adding to the gravity force of the flapper weight that tends to move it to the open position. Another magnet can be used to urge the flapper to the closed position. U.S. Pat. No. 7,828,066 transmits power through a magnetic shaft coupling. U.S. Pat. No. 3,264,994 shows the use of a magnet on a dart that is pumped past a tool to use the field to trigger tool actuation. US Publication 2010/0126716 illustrates a hard wired system for initiating tool actuation using a magnetic field. Other patents of interest with regard to the present invention are: U.S. Pat. Nos. RE 30,988; 7,703,532; 7,669,663; 7,562,712; 7,604,061; 7,626,393 and 7,413,028.